1. Field of the Invention
The present invention relates to a control system for a refrigerator, or more in particular to a control system suitable for rapidly freezing the contents of a refrigerator.
2. Description of the Prior Art
A conventional freezing device has been suggested of which the freezing capacity is variable by stepless control of the rotational speed of a compressor, as disclosed in Japanese Patent Publication No. 26294/79.
The conventional refrigerators with variable freezing capacity, of which those having the ability to control the rotational speed of the compressor steplessly are highest in efficiency, have the disadvantages as mentioned below.
Since the speed control of the motor for driving the compressor requires a driving unit or an inverter, the total efficiency of the speed control motor is given by a product of the efficiency of the inverter and that of the motor proper. Therefore, the total efficiency of the motor is reduced in operation at its rating capacity below the efficiency of the motor when directly driven by commercial frequency at the rating. As a result, the efficiency of the whole refrigerator with variable freezing capacity is decreased.